Approved — US FDA (2026-10-08) Japan — application under review (not approved)
Colon cancer immunotherapy has moved into the post-surgery (adjuvant) setting for the first time. On October 8, 2026, the US FDA approved the immune checkpoint inhibitor atezolizumab (Tecentriq) together with standard FOLFOX chemotherapy for patients with completely resected stage III dMMR (MSI-H) colon cancer. In the phase 3 ATOMIC trial, the risk of recurrence or death was roughly halved compared with chemotherapy alone (hazard ratio 0.50), but an overall survival difference has not been shown, and in Japan the drug is still under review for this use.
What was approved: adjuvant immunotherapy after colon cancer surgery
For stage III colon cancer, the long-standing standard after surgery has been about six months of oxaliplatin-based chemotherapy (such as FOLFOX) to reduce recurrence. The new approval adds atezolizumab, an antibody that blocks PD-L1. It is given with chemotherapy for six months, then alone for another six months — about one year in total.
The FDA approved both the intravenous form (Tecentriq) and the subcutaneous form (Tecentriq Hybreza). The application received Priority Review and was reviewed under Project Orbis, with concurrent review by regulators in Australia, Canada, Israel and Switzerland; the FDA said those reviews were ongoing.
Who is eligible: stage III dMMR / MSI-H colon cancer
This is not for every patient with colorectal cancer. All of the following apply:
- Stage III colon cancer (spread to lymph nodes but not to distant organs), with the primary tumor completely removed by surgery
- The tumor tests as dMMR (deficient DNA mismatch repair) — the cell's system for fixing DNA copying errors is broken. Depending on the test, this is also called MSI-H (microsatellite instability-high).
- Per the FDA label: the IV form for adults and children aged 2 years and older; the subcutaneous form for patients aged 12 and older weighing at least 40 kg
Roche states that about 15% of colon cancer patients have dMMR/MSI-H tumors, and Chugai reports a dMMR rate of 6–7% in colorectal cancer in Japan. Check first whether your pathology report includes an MMR or MSI result. The approval wording covers colon cancer; whether it applies to rectal cancer should be confirmed with your doctor.
ATOMIC trial results and side effects
The evidence comes from ATOMIC (NCT02912559), a phase 3 randomized trial run by the Alliance group with National Cancer Institute (NCI) support. A total of 712 patients (including one child) were randomized 1:1 to chemotherapy plus atezolizumab or chemotherapy alone. Results were published in the NEJM in March 2026 (lead investigator Frank Sinicrope, Mayo Clinic).
| Measure | Atezolizumab + mFOLFOX6 | mFOLFOX6 alone |
|---|---|---|
| 3-year disease-free survival | 86.3% | 76.2% |
| DFS hazard ratio | 0.50 (95% CI 0.35–0.73) | |
| 5-year overall survival | 89.7% | 87.9% |
| OS hazard ratio | 0.90 (95% CI 0.55–1.47) — not statistically significant | |
| Grade 3–4 adverse events | 84.1% | 71.9% |
Sources: NEJM 2026;394:1155-1166 (as reported by The ASCO Post and Chugai), FDA approval notice. Median follow-up for DFS 40.9 months.
In short, adding immunotherapy meaningfully reduced recurrence, but no overall survival difference has been shown during follow-up so far. Side effects also increased: severe (grade 3–4) adverse events occurred in 84.1% vs 71.9%. The most common were low neutrophil counts, peripheral sensory neuropathy (numbness in hands and feet) and fatigue. Two treatment-related deaths (sudden death and sepsis) were reported in the atezolizumab arm. The FDA label warns of immune-mediated adverse reactions (inflammation of the thyroid, lungs, liver, bowel and other organs) and infusion-related reactions.
In an exploratory analysis, the benefit was clear in patients who received more than six cycles of FOLFOX (HR 0.41) but not evident with six or fewer (HR 0.97). As a subgroup analysis, this is not a firm conclusion.
Where it is available: approved in the US, under review in Japan
- United States: FDA approval on October 8, 2026 (approved treatment).
- Japan: Chugai filed with the Ministry of Health, Labour and Welfare on August 14, 2026 for adjuvant treatment of MSI-High colon cancer. As of the date checked, it is not yet approved in Japan. Chugai says it would be the first immune checkpoint inhibitor in Japan for this use if approved.
- Europe and others: Roche says it is pursuing further filings, including with the European Medicines Agency; Australia, Canada, Switzerland and Israel are reviewing it under Project Orbis.
Use in a country where it is not approved for this purpose may not be covered by insurance, so check approval status and costs first if you are considering treatment abroad. For translation of Japanese medical documents or on-site interpretation, see Contact FTH.
What to check and questions for your doctor
- What is my tumor's MMR (or MSI) result? If it has not been tested, can it be done now?
- Is my cancer definitely stage III, and is it colon or rectal cancer?
- Compared with chemotherapy alone, what benefit and extra side effects should I expect in my case?
- Do I have conditions, such as autoimmune or thyroid disease, that call for caution with immunotherapy?
- What tests will I need during the one-year treatment, and how often?
Frequently asked questions
Does immunotherapy work for all colon cancer?
No. This approval is for patients with stage III colon cancer confirmed as dMMR (MSI-H) after surgery. The results cannot be applied directly to the more common pMMR (MSS) colorectal cancers.
Does atezolizumab help patients live longer?
It roughly halved the risk of recurrence or death, but no statistically significant overall survival difference was seen in the reported follow-up (5-year 89.7% vs 87.9%). Longer follow-up is needed.
Can I get this treatment in Japan?
As of October 14, 2026, it is under review in Japan and not yet approved. Check announcements from the Ministry of Health, Labour and Welfare, PMDA or Chugai for the approval status.
How common are side effects?
In ATOMIC, grade 3–4 adverse events occurred in 84.1% of the atezolizumab group and 71.9% of the chemotherapy-alone group. Immune-related side effects can appear even after treatment ends, so report symptoms to your care team promptly.
Related: Selective intra-arterial chemoradiotherapy for tongue cancer · Preparing for interpretation before a visit to Japan · Other Japanese medical information
Sources
- U.S. FDA — FDA approves atezolizumab in combination with chemotherapy for Stage III mismatch repair deficient colon cancer (2026-10-08)
fda.gov
Checked on: 2026-10-14 - Sinicrope FA, et al. Atezolizumab plus FOLFOX for Stage III Mismatch Repair–Deficient Colon Cancer. N Engl J Med 2026;394(12):1155-1166
doi.org/10.1056/NEJMoa2507874
Checked on: 2026-10-14 - 中外製薬 — テセントリク、MSI-Highを有する結腸がんに対する術後補助療法として適応拡大申請 (2026-08-14)
chugai-pharm.co.jp
Checked on: 2026-10-14 - Roche — FDA grants Priority Review for Tecentriq for a certain type of stage III colon cancer (2026-06-11)
roche.com
Checked on: 2026-10-14 - ClinicalTrials.gov — ATOMIC (NCT02912559)
clinicaltrials.gov/study/NCT02912559
Checked on: 2026-10-14
Written by the FTH editorial team. Sources checked 2026-10-14 · Medical review: not applicable
This article is general information based on public sources and does not replace diagnosis or treatment. Please discuss treatment decisions with your medical team.
